Tools for compressing image sequences are often designed to encode integer data with a limited dynamic range. For example, compression standards, such as MPEG-4 AVC/H.264 and HEVC (High Efficiency Video Coding), can be used to compress images and videos whose color components are represented by 8 bit integers. In extended versions of these standards, data with higher bit depths can be taken as input. For example, in the Range Extension version of HEVC, a bit depth up to 16 bits is supported. The high bit-depth extensions may require increased implementation and computational costs. Moreover, for some applications such as 3D computer graphics, there also exist image types whose bit depth is higher than 16 bits.
An alternative solution for encoding high bit-depth images is to apply a tone mapping operator (TMO) on the HDR images to reduce the bit depth and to generate a Low Dynamic Range (LDR) version of the HDR images. A low bit-depth encoder can then be used to compress the LDR version. In this approach, the TMO is usually invertible and the inverse tone mapping should be known to the decoder. An example of this approach is described in an article by Z. Mai et al., titled “On-the-Fly Tone Mapping for Backward-Compatible High Dynamic Range Image/Video Compression,” ISCAS 2010, which defines a tone mapping curve that minimizes the data loss caused by both the tone mapping and the encoder error.